The elucidation of mechanisms of secondary brain injury (the molecular and neurochemical events that occur following impact) which contribute to the morbidity and mortality of victims of severe traumatic brain injury is best accomplished through basic science investigations using animal models of TBI. However, species-specific differences in the type and relative importance of these mechanisms must be considered prior to assuming that mechanisms found to be important in rodents contribute significantly to human secondary injury. Failure to consider and investigate this possible is one likely explanation for the inability of several recent clinical trials to demonstrate efficacy of their study drug after it showed promise in animal studies. The Clinical Core will enable the investigations of the five primary projects to correlate the findings of their basic science investigations in animal models with mechanisms of secondary brain injury in human victims of TBI by: 1. providing appropriately processed and preserved specimens of CSF, dialysate collected during microdialysis of the extracellular space, and brain tissues removed at the time of surgery for evacuation of contusions, 2. assuring high quality, consistent acute care of these patients, 3. providing comprehensive functional and neuropsychological follow-up information about these patients at 3,6 12, and 24 months after injury, and 4. maintaining a detailed clinical database for all of these patients.